X-rays, from www.icufaqs.org Mark Hammerschmidt, RN

It’s just my opinion, but I think that ICU nurses should have some basic (really basic) idea of how to look at x-rays of some of their “tools of the trade”: ET tubes, central lines, PA lines, maybe a couple of others. Obviously you aren’t going to be trying to compete with physicians in reading them, but still I think it’s useful to be able to look at a stat film and say “Gee, it looks like that ET tube is in the right main stem.” Or “Wow, no wonder the PA line is stuck in wedge, look how far in it is!” Things like that. So I went out on the web and surfed around, and I found some film images that may be helpful.

As usual: please remember that this material is not meant to be an official reference of any kind – it’s supposed to reflect the experience and knowledge of a preceptor as it is passed on to a new RN orientee. Also please let me know when you find errors or omissions – we’ll put them in right away.

A word about the x-ray images: film images can be impenetrably hard to read, even if you have, as radiologists are said to have: x-ray vision. (Ha!) A lot of these images areclearer on the computer screen, I guess because the resolution is lots higher than what’sproduced by most printers. Mine, anyhow. Try a laser printer, or try looking at the pictures on your monitor and adjusting the contrast - sometimes it helps.

1- What is an x-ray?2- What are some common x-ray procedures that my patients may have in the MICU?3- Who takes x-rays?4- Who reads them?5- What is a stat film? How stat should stat be?6- Can I stay in the room if my patient is being x-rayed?7- What are those clip things that the x-ray techs wear?8- It seems like my patient has been x-rayed twelve times today – is that safe?9- Who was Roentgen?10- Is it true that Marie Curie glowed in the dark?11- What about Pierre?12- What is a CAT scan? What is a spiral CAT scan? How long to CT scans take?13- What is a CTA?14- What’s the difference between a CT scan and an MRI?15- What is an MRA?16- Why do some tests use contrast?17- What’s the connection between IV contrast and renal failure?18- What is this I hear about mucomyst?19- Do we give contrast in the MICU?20- What kind of IV access does my patient have to have to get IV contrast?21- What about Gastrografin?22- What is the problem with Glucophage (metformin)?

List of X-ray Images:

a- Normal chest film with markersb- Chest film with a really clear trachea and carina.c- Chest film with ETT and NGTd- ETT in the right mainstem.e- The same ETT pulled back to proper positionf- Chest film with ETT, and CVP line, and maybe an NG tubeg- Chest film with a trach in place, and old sternotomy wire sutures.

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h- A non-tension pneumothorax.i- Tension pneumothorax with a really neat mediastinal shift.j- Another tension pneumo.k- An NG tube causing a pneumothorax.l- A big pleural effusionm- A chest film with two chest tubes: one’s in position, the other isn’t.n- A PA lineo- A PA line with an interesting object nearbyp- An IABP tip (you sure?), and a PA line, probably not in far enough.q- An abdominal film with dilated bowel loopsr- One patient, two films, before and after developing tamponade.s- Who is this, and what happened to him?t- The first-ever CVP line.

1- What is an x-ray?

Here’s what I know – I mean, I could look up all sorts of information, but this is supposed to be what your preceptor knows, right? Is your preceptor a medical physicist? No! But can your preceptor work an intra-aortic balloon pump, a CVVH machine, and a Zoll pacing box (how about one at a time, okay?) Hopefully!

So: x-rays are a kind of dangerous but useful ionizing radiation. They produce images on silver-coated film that lives in the x-ray plates that we’re forever putting behind one part of our patients or another.

The dangers in exposure to x-rays are two: how much power they use to shoot, and how close you are to the shot. “The exposure varies inversely with the square of the distance from the source.” Meaning: that your risk of exposure drops a whole lot when you get away from where the machine is pointing at. So stand way back. I usually stand behind the tech shooting the film (grin!).

2- What are some common x-ray procedures that my patients may have in the MICU?

Our patients get “imaged” a lot. Most of our images are portables, shot in the bed, although all too often patients will have to travel to the radiology suites for CT or MRI studies. Some common situations:

“Plain films”:

After intubation. After the insertion of any central line in the neck or chest, or after repositioning a

line. After the insertion of a chest tube. After the insertion of a soft nasogastric tube – in fact, I hear that nowadays

there’s a push on to get a film after the insertion of Salem sump tubes as well, which to me doesn’t seem to make sense if you’re getting gastric materials from it, although it might just be in the distal esophagus…

Whenever your patient looks like they’re in worsening respiratory distress. To help evaluate “before” and “after” treatment of pulmonary edema. Daily to evaluate changes in, say, pneumonia, or any other developing disease

process. Rarely, we’ll have bone-fracture films to shoot, but usually fractures in our

patients are stabilized in the most basic way by orthopedics, and then left to be resolved once the more life-threatening problems are settled.

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CT scans and MRI’s: (starting from the top and working south, and only listing the ones that come readily to mind)

Head : Any kind of acute neuro event, or symptoms of a neuro event, will often buy your patient a head CT. In CVAs, the critical question is: is it embolic, or hemorrhagic?

Neck and spine : usually a traumatic neck injury can be “cleared for c-spines” with plain films, but now and again you’ll see a CT or MRI for these. Encephalitis and meningitis also show up nicely on CT’s, I understand.

Chest : lots of reasons for chest scans – traumatic injuries, bleeds, tumors, fluid collections…

Abdomen : also lots of reasons – specific organ disease, fluid or air collections, retroperitoneal bleeds (we see our share of these – lots of our patients get “hardware-ized" in one fem or the other).

Pelvis : Also for looking at retroperitoneal bleeds, I believe – in the MICU anyhow. SICU patients might have an unstable pelvis after a car crash.

3- Who takes x-rays?

X-ray techs shoot all our films. There are specialty techs who run the CT scanners and the MRI machines. I believe that there is a single tech who does all the portable CT scans. Don’t forget though, that on trips to the scanners you are the person in charge of the patient clinically. If you think there’s a problem, or the chance of a problem – speak up! The techs are used to this, and are more than willing to help you get the patient through the scan safely. There’s a detailed “trip to the scanner” section in the “New in the ICU” FAQ.

4- Who reads them?

Our house officers do quick reads on stat films, but if they have any questions about what they’re looking at, there’s always a radiologist available in the house to help them out. All the films are reviewed on radiology rounds within 24 hours.

5- What is a stat film? How stat should stat be?

This can vary a lot, depending on how busy the techs are. Stat in my mind really ought to be within 30 minutes at the most. Sometimes it just takes longer…

6- Can I stay in the room with the patient if my patient is getting x-rayed?

I find that I rarely need to – the only time I can think of is if the patient is having lateral decubitus films shot (side-lying – they’re usually looking to see if a collection of fluid moves downwards with gravity and “layers out”). It can be hard to keep a patient in this position when they’re hooked up to lots of hardware – check with the tech - you may find yourself wearing lead and holding the patient up.

By all means, use appropriate measures to safely, briefly sedate your patient if she needs it for the x-ray. If you’re taking your patient off the floor for CT or an MRI, check with the team –

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if your patient can’t be accurately scanned because of agitation, there’s no point in making the trek if you can’t safely give them sedation to help them hold still.

7- What are those clip things that x-ray techs wear? Should we wear them?

The techs all wear film dosimeters – gadgets that measured their cumulative exposure to radiation over some given period of time. As for nurses wearing them – I need to ask around about this. (Update – the techs said no.)

8- It seems like my patient has been x-rayed twelve times today – is that safe?

It’s obviously a question of priorities: will the patient benefit more from having the x-ray studies, or from not having them? Looking around on the web I found an interesting way of looking at the problem: you compare the amount of radiation from the x-ray study with the amount of normal “background” radiation the patient might receive just by lying still in bed, bombarded by cosmic rays, and radon from the rumpus room in the basement. They call this the “Background Equivalent Radiation Time” – or BERT. Here are some of the numbers:

Dental x-ray: 1 weeks’ worth of normal background radiation. Chest film: 10 days. Upper GI series: 1.5 years (uh-oh…) Lower GI series: 2 years I understand myself that KUBs use a lot more radiation than chest films do – I

always stood way back when we were having our kids…

The website giving this information went on to say that “no studies of radiation to humans have demonstrated an increase in cancer at the doses used in diagnostic radiology…”. I’m obviously not trying to do a comprehensive review here – but as far as I went, the information was reassuring. Your milage may vary…

9- Who was Roentgen?

Worth mentioning – he discovered that these strange rays generated by his vacuum tube could pass through certain materials, make interesting images on silver-coated photographic plate. Not knowing what the rays were or where they came from, he called them “X” - like the unknown quantity in an algebra formula.

Here he is:

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The second picture is of Mrs. Roentgen – part of her, anyway – maybe the first or second x-ray ever taken.

10- Is it true that Marie Curie glowed in the dark?

Neat rumor, huh? My daughter did a report on Marie in high school, and says that to this day they still can’t handle her diaries – they’re too radioactive.

11- What about Pierre?

I have no idea, but my daughter says there’s an old joke:

Pierre: (going to bed at night) Marie, turn the lights out.Marie: They are out, dear.

12- What is a CAT scan? What is a spiral CAT scan? How long do scans take?

Nurses have a pretty good idea of what CT scans are – they produce a series of “cuts”, images across the body working upwards or downwards through the body section in question.

Spiral CTs are a newer kind of scan – the scanning tube rotates continuously as the patient moves along through the scanner – the result is better imaging with lower radiation exposure. Most scans nowadays take less than half an hour – it’s transporting your possibly unstable patient to the scanner and back that makes for all the stress. There’s a full description of how you might plan and carry out a trip to the scanner in the “New In the ICU” FAQ.

13- What is a CTA?

CTA stands for CT Angiography – the idea is to do a spiral CT scan while IV contrast is injected. CTA can apparently require a lot of contrast – 100-150 ml. This may be a bad thing for your patient’s kidneys…CTA seems to be the scan of choice when evaluating PE’s and vascular aneurysms of one kind or another.

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14- What’s the difference between a CT scan and an MRI?

MRI stands for Magnetic Resonance Imaging – it uses radio-frequency waves instead of ionizing radiation to generate an image. The machine involves the use of very powerful magnets – they will pull anything made of ferrous material (iron/steel) right off of you into the machine, and you will not be able to get it out until the techs shut the magnets down – this usually makes them very unhappy. There was a famous story from somewhere about a code cart getting whipped entirely up off the floor…

Likewise, taking a patient with implanted objects can be very dangerous – how about pacemakers? Hip replacements? Cerebral aneurysm clips? Think about this every time you take a patient to the MRI suite – check with the team, and check with the scanner techs to make sure the scan is safe.

MRI scans take much longer than CTs – get orders for appropriate sedation (I find a little propofol in my coffee is very helpful – ow! Oh, you meant the patient!) before you go. Here are a couple of nice images to show the difference in quality:

15- What is an MRA?

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This is a CAT scan of - what? And what’s that thing over there on the left? At least it’s not pushing everything over to the other side…

Look a little clearer? Same patient. This is an MRI with gadolinium contrast. The difference is that this is a much more expensive study. I know which one I want my brain surgeon looking at…

MRA is “Magnetic Resonance Angiography” – which is to say, MRI looking at blood vessel flow, probably using contrast. MRI studies use a contrast material called “gadolinium” - you’ll hear the techs say things like: “With or without gado?” Gadolinium turns out to be an element – here’s what I could find out about it: “Gadolinium, chelated to a carrier molecule, is an intravenously injected MR contrast agent which …normally stays in blood vessels…it has the effect of making vessels, vascular tissues, and areas of blood leakage appear brighter.” (Thanks Ray Hsu, Washington U. School of Medicine!) So this is what you’ll probably see them give when you’re looking for a bleed somewhere… “Gadolinium is excreted through the kidneys, with a half –life of 1.25 – 1.6 hours.” Gado has the reputation of being very low on the allergic reaction list.

16- Why do some CT tests use contrast?

They help light up the structures that you’re trying to see. In CT scanning, the contrast dye is iodine-based – which is why patients with allergies to shellfish aren’t supposed to get them. These dyes definitely have dangers associated with them: obviously, some people are going to have severe allergic reactions. The other problem, and we see this one more often than we’d like to, is the fact that a dye load can really, seriously hurt a patient’s kidney function, especially if they’ve got some degree of renal failure already. Here are some of the main points:

IV contrast dye can cause reaction that is about the same anaphylaxis, and is treated the same way. If a patient reacts it has nothing to do with previous exposure to the dye.

Reactions occur in less than 5% of the patients who get IV contrast dye. There’s an alternative “low-molecular weight” dye that lowers the risk of reaction to less than 1%.

Hives is what most people show as a reaction to contrast.

The risk of a fatal reaction is something less than 1 in 100,000.

Pretreatment helps. Antihistamines and corticosteroids, as well as using “non-ionic, low molecular weight” contrast dyes means lower rates of anaphylactoid reactions. The reaction may not be related to previous exposure, but people who have reacted before may react again – the rate is 17-60%. Asthmatics and people with multiple allergies are at greater risk for reaction.

Severe reactions are very rare… 1 in 6250 exams using LMW contrast.

17- What is the connection between iodine-based contrast and renal failure?

Here I’m going to summarize one of a really neat series of clinical pearls from the US Army Pharmacy website, edited by Major Dave Andersen. This one was comprehensive yet succinct, and extremely clear. Thanks, Major Andersen.

A 62-year old patient with diabetic nephropathy is booked for a CT scan with contrast. All labs are normal except for a glucose of 135, and a creatinine of 2.4. (Uh-oh…I’ve been in too many of these situations myself. Can you spell CVVH?) The radiologist is concerned about giving contrast to a patient with a creatinine over 2.0. Is there anything that can prevent or minimize further kidney damage?

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Acute renal failure from IV contrast – this they define as a rise in creatinine of more than 0.5 within 48 hours after the dose – ranges from 9-40% in diabetics with mild-to-moderate renal insufficiency, to 50-90% in diabetics with severe chronic renal insufficiency. (Ack! I take my glucophage, don’t I? And the doc says my feet tingle because I stand up all night…)

Some summary points:

Lots of things have been tried.: Ca+2 channel blockers, mannitol, lasix, dopamine, others, with little or no success. “Mannitol and furosemide actually worsened renal function more than saline alone.”

The problem is that CT scans of many areas are basically worthless without contrast. (How about going straight to MRI instead? Or is there no advantage?)

Non-ionic, LMW contrast may cause less kidney damage.

IV hydration before and after a contrast dose is shown to limit kidney damage. Normal or half-normal saline at a rate of 1ml/kg/hour for 12 hours before, and 12 hours after the contrast seems to be effective.

18- What is this I hear about mucomyst?

A recent study (NEJM 2000 43: 180-4) showed that a 600mg dose of Mucomyst (acetylcysteine) on the day before and the day after the contrast dose significantly lowered the incidence of contrast-induced acute renal failure. Anybody know how this works?

19- Do we give contrast in the MICU?

We give oral contrast in the form of gastrografin. The CT orders have built-in dosing orders to tell you what to do – usually it’s something like 7.5cc of gastrografin in 200cc of water either orally (ack!) or through an NG tube, repeated several times. Check with the team if you’re worried about your patient’s kidneys.

20- What kind of IV access does my patient have to have to get IV contrast?

We take patients with all sorts of IV access to the scanners, but for some reason the techs down there want the patient to have a plain, garden-variety heplock in one arm or the other. Anybody know why they don’t use a central line? Make sure the IV is patent, and in a sizable vein – that contrast gets injected pretty fast…

21- What about Gastrografin?

Appaarently this stuff is very safe to use. It is iodine based.

22- What is the problem with Glucophage (metformin)?

(I took a personal interest in this one…) Glucophage has the rare but unhappy ability of provoking a severe lactic acidosis, especially in renal failure situations. If the IV contrast dose were to push a patient from, maybe, CRI to ARF, then the presence of glucophage in that situation would be a bad thing. It appears that the routine is to hold glucophage for a day before the exam, and for two days afterwards… good to know.

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a- Normal Chest Film with Markers

..

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Here’s the trachea, nicely at midline.

The carina ought to be around here.

I was taught that a line is “central” if the tip is inserted beyond the third rib. Is this the third or fourth, behind the clavicle?

If the CVP tip is this far down, it needs to be pulled back to the SVC.

Not much of a bubble. Sometimes they look like a big clear volleyball. You can decompress a big stomach bubble with an NG tube.

These are the two “hemi” diaphragms. Sometimes one or the other is pushed down, or pulled up, for one reason or another.

Don’t you think that arrows and text boxes are just the most artistic thing since Leonardo? (My son showed my how to make them.) Imagine what they could do for the Mona Lisa! Hey, yo, Louvre, what do you say?

b- Chest film with a really clear trachea and carina.

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This film shows the trachea, carina, and main stems very clearly – they’re not always so easy to see.

Here’s the carina. An ET tube that’s too far in may poke the carina – this may be why your patient is hacking and choking all the time.

The right main stem is where patients often aspirate to - it's more in a straight vertical line downwards than the left one. ET tubes that are advanced too far also usually wind up here.

This is a pretty unpleasant looking x-ray. Compare these fluffy looking lung bases to the nice clear ones in the first picture – probably pneumonia. See how the left hemidiaphragm has been pulled upwards? That’s a pneumonia thing.

c- Chest film with ETT and NGT

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Pretty sure this is the carina.

I may be seeing things, but I’m pretty sure this is the end of an ET tube. A little too high, I think.

This looks like the radio-opaque line on a nasogastric tube. It looks just like the EKG monitoring wires, but it has no electrode connector at the end, and it’s in the typical place.

Here’s an electrode wire with a connector at the end.

d- Endotracheal tube in the right main stem.

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Something definitely wrong with this picture. Does this patient have lung sounds on the left after being intubated? No? I wonder why her sat is so low…

This is the carina. I think.

Here’s the left main stem. Any air getting into this lung?

e- ET tube pulled back to the proper position.

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The web site said that this was the same patient, after the tube had been repositioned (pulled back.) I’m not sure. But anyhow this person’s ET tube isn’t in either main stem, and the left lung looks nicely aerated. (I can’t see the carina either.) What kind of central line does this patient have – meaning, is this in the internal jugular, or the subclavian, or (hey, let’s be creative) is it maybe a femoral line? Is the tip where it ought to be?

f- Chest film with ETT, CVP line, and maybe an NG tube.

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I have no idea why this image came out reversed, but there are a couple of things for you to try to find: ET tube look all right to you? What kind of central line does this patient have? Tip position okay? Is there an NG tube?

g- Chest film with a trach in place, and old sternotomy wire sutures.

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Here’s a short trach tube.

See the sternal wires? S/P CABG or valve.

h- A non-tension pneumothorax.

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All the normal fuzzy stuff here on the left are what they call “vascular markings”.

Are there any vascular markings here? Where’d they go? Why is this whole area very clear? (The word is “hyperlucent” – which I believe translates as “very clear”).

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Lots of vascular markings on this side.

Where’d the markings go?

This is definitely a much more dangerous situation than the one before it. This time, the pressure on the pneumo side has steadily increased, and now the heart is getting shoved forcibly over to the other side – definitely classed as a “big bad thing”. Which service would you stat page to come see this patient?

Everybody knows how to set up a chest tube, right? And you all know what an air leak is? What maneuver could you make before the surgeons arrive?

If this patient had an arterial line, you might see a nice example of “pulsus paradoxus” – blood pressure that drops with inspiration, and rises with expiration – in fact, this might be your first clue that a tension pneumo might be developing. Take a look at the “Chest Tubes” FAQ for more on this …

i- Tension pneumothorax with a really neat mediastinal shift. (I guess the patient doesn’t think it’s so neat…)

Does everybody know the procedure for inserting an IV catheter into the chest to decompress a pneumothorax? Where does it go? Who puts it in? How far in should it go? What should you hear; and then maybe see the patient do? Fly around the room backwards?

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Definitely having too much fun with the arrows…

Why is this hemidiaphragm being pushed downwards?

Another really nice image from the Virtual Hospital.

Not a pretty picture, however. See the pneumothorax down there at the bottom? Actually, is there one on each side?

So, uh, did they never hear the phrase: “Stop when you feel resistance!”?

j- Another tension pneumo.

k- an NGT causing a pneumo. Looks like a Dobhoff.

m.- A chest film with two chest tubes: one’s in position, the other isn’t.

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Pretty big effusion over there on the patient’s right. What should we do?

The break in the line shows where the suction tube has a side port. What happens if the tube gets pulled on, and the port gets outside the skin?

Doesn’t look right. What noise might you hear when you get close to this patient? How could you use sterile vaseline gauze to put a temporary fix to this situation? Who needs to be called?

l.- A big pleural effusion.

Looking at the chest tube on the left – see the break in the line that travels along the side of the tube? That’s where the drainage port is. Suppose that chest tube is hooked up to suction through a pleurevac box – what might you hear while standing close to the patient? What could you do about it as a temporary fix? What team would you call if you found this situation, and what would you have ready for them when they came?

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Awful picture, but you can see how the PA line curls around as it goes through the RA, the RV, and up around into the PA. My arrow is pointing to where I think the tip is - I think this line is probably not quite far enough in, and won’t wedge. If the PA line were to slip back, say, to the RV – how might you know? What would you do about it?

That’s more like where a PA tip ought to be. I had to play with the contrast in this image to make the line a little clearer, so it’s very dark. Any guesses as to what the white arrow is pointing at? What if I were to tell you that maybe the laryngoscope operator was a little hasty during intubation? Should we call the dentist if the patient codes?

n- a PA line.

o.- A PA line with an interesting object nearby.

p- An IABP tip. (Really?), and a PA line, probably not in far enough.

q.- An abdominal film with dilated bowel loops.

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The story here was that the black arrow is pointing at the tip of an intra-aortic balloon pump. I think I see sternal wires, and my arrow I think maybe is pointing to the really misplaced end of a PA line, but I don’t see any balloon tip. Which doesn’t mean it isn’t there…

We don’t spend all our time looking at the chest, you know. Has your patient been on a fentanyl drip? Gas collection can cause the bowel to distend for all kinds of reasons…time for Reglan? Or a surgeon?

r.- One patient, two films, before and after developing tamponade.

Here’s a little sample of electrical alternans:

http://ecglibrary.com/elec_alt.html

And here’s a sample of what pulsus paradoxus looks like on an a-line tracing:

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What a difference two months makes! Bet this patient had some rub! That’ll teach you not to forget your Indocin! There are three situations where you might see a clear pulsus paradoxus on your a-line wave, and this is one of them: pneumothorax, pericardial tamponade, and really severe dehydration/hypovolemia. Which one is this? The other clue is something you only might see now on the EKG monitor: “electrical alternans” – the QRS complexes are alternately big, then small, then big, then small. They may get a liter (!) out of this patient’s pericardium…that’s a portacath, right?

s.- Who is this, and what happened to him?

Copyright materials used with permission of the author and the University of Iowa's Virtual Hospital: www.vh.org.

Thanks Iowa! (“Is this heaven?”, “No, it’s Virtual Iowa…”).

t- The first-ever CVP line.

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Any ideas? This turns out to be the “Iceman” – the poor guy that was found after being frozen for so long on that glacier in Switzerland. The pointed object in the yellow ring turns out to be the arrowhead that killed him. I thought the Swiss were neutral…

See it there, in white, coming up the left arm? This is apparently the original famous photograph taken by Werner Forssmann, back in 1929. Apparently in the grip of enthusiasm, he threaded a urologic catheter upwards into his own arm, then ran downstairs to the x-ray room where he got into a scuffle with a colleague who thought he was going nuts, kicked him in the shins to get by, and then shot this film. The rest, as they say, is – “Hey, would you just throw in a central line already? I can’t keep this guy on peripheral neo forever, y’know!”

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